Maximizing link capacity represents an important aspect of advancing the performance of wireless communication systems. The link scheduling provisions in developing standards, such as the Enhanced Uplink (EUL) in Releases 6 and 7 according to the 3rd Generation Partnership Project (3GPP) Universal Mobile Telecommunications (UMTS) specifications, reflect this aspect of wireless communication evolution. Other standards similarly define scheduled transmission environments, such as the CDMA2000 standards, and selected Wireless Local Area Networking (WLAN) standards.
Uplink (also referred to as “reverse link”) scheduling within a given radio coverage area, e.g. cell, permits one or a constrained number of users to transmit uplink data (traffic) in any given scheduling interval. Allowing only one user, for example, to transmit uplink data in any given scheduling interval prevents other user's uplink data transmissions from interfering with the scheduled user's data transmission, and effectively devotes the available uplink capacity to that user. Doing so maximizes the uplink data rate achievable by the scheduled user.
Of course, scheduling may be more sophisticated, such as by scheduling multiple users in the same interval, but perhaps with only one or two high-rate users permitted. Further, any given user may be permitted to transmit at essentially any time on an unscheduled basis, but these types of unscheduled transmissions may be constrained to a low data rate, for example. Consequently, unscheduled transmissions of this type, even if permitted, may not represent a significant source of uplink interference and the interference level does not change abruptly over time.
According to the EUL provisions mentioned, individual mobile stations operating as packet data users subject to uplink scheduling transmit a Dedicated Physical Control Channel (DPCCH) signal when transmitting scheduled data and when not transmitting scheduled data, although the signal may be gated in the latter instance. A supporting base station thus receives a DPCCH signal for each scheduled user and uses the quality of that received signal as a basis for maintaining closed loop control of each user's uplink transmit power.
As is known, such power control usually includes an inner and outer power control loop for each user. The outer loop power control sets a signal quality target, e.g. signal-to-interference ratio (SIR) target, and the inner loop power control generates up/down commands as needed, for increasing and decreasing the user's uplink transmit power as needed to maintain the signal quality at the base station for that user at the signal quality target. Outer loop power control also adjusts the signal quality target of the inner loop power control in order to maintain a specified communication quality-based target (e.g. Block Error Rate (BLER) or number of transmission attempts).